Vehicles such as an automobile requires a vehicle structure with which transmission of vibrations, generated in various portions of the vehicle, into a vehicle cabin is suppressed as much as possible, to achieve a favorable riding comfort felt by a passenger. To satisfy the requirement, the present applicant has proposed techniques of achieving a sophisticated joining mode between a bulkhead (reinforcement member), disposed in a frame forming a closed section, and the frame in Patent Literature 1, 2, and 3. The joining mode features the frame provided with: a rigid coupling portion in which the frame and the bulkhead are coupled with each other while being in contact with each other; and a flexible coupling portion in which the frame and the bulkhead are coupled to each other with a damping member in between.
The vehicle includes a portion having a partitioned closed section structure, and including: two panels (frames) forming a closed section extending in a predetermined direction; and a partitioning panel that is disposed in the closed section and extends in the predetermined direction. Patent Literature 3 discloses a vehicle-body structure obtained with a bulkhead, including the rigid coupling portion and the flexible coupling portion, incorporated in the portion having the partitioned closed section structure described above.
For example, the partitioned closed section structure is employed in a coupling portion between a center pillar and a side sill, or the like. The coupling portion involves an especially high requirement for suppressing deformation and vibration of the closed section portion due to vibration of the vehicle.